Exertiona

Exertiona is a fictional biomolecule used in science fiction and academic thought experiments to explore the biology of exertion and endurance. It does not correspond to a known chemical substance, and there is no empirical evidence of its existence in humans.

The term derives from exertion and the common biological suffixes used for molecules. In various works, exertiona is depicted as a signal produced by contracting muscles during high-intensity effort, capable of diffusing within tissues and influencing distant organs, including the brain and skeletal muscles.

In-universe mechanisms are often described as exertiona modulating neural perception of effort, accelerating energy production in mitochondria, or shifting fuel use toward more efficient pathways. Some portrayals invoke fictional regulators or receptors and contrast exertiona with countervailing signals, creating a narrative framework for how physical performance might be amplified or regulated.

Applications of the concept appear as plot devices to explain sudden bursts of endurance or to examine potential consequences of heightened exertion, such as fatigue rebound or metabolic imbalance. It is also used pedagogically to illustrate how signals between muscle and brain could hypothetically influence performance without asserting real-world feasibility.

Real-world stance: Exertiona is not recognized by pharmacology or physiology as a genuine substance. In fiction and educational contexts, it serves as a hypothetical construct to discuss energy metabolism, fatigue, and the psychology of effort, without implying any verified or safe intervention.